Error 11 is thrown whenever you're trying to activate a key that is already active on two other PCs at this time. As per our End User License Agreement, each key can only be used on up to two PCs at the same time.
In order to use the same key on a third PC, you need to first UNLICENSE one of the previously activated games. [Click here to find out how to unlicense.]
Other common eLicense errors [are listed here.]